Two lever print actuator with aligned pivots and energy transfer surfaces

Abstract

A two-lever electromagnetic print actuator having a pivoted bellcrank armature and an end-pivoted print hammer is urged to free-flight by energy transfer at an energy transfer contact surface. The armature pivot, print hammer pivot and energy transfer surface are aligned in sequence and substantially coplanar. This converts input energy to optimum print velocity with minimum wear. In operation, energizing a coil attracts the armature to the stator, imparting energy to an energy transfer surface on an energy transfer armature leg. The energy transfer surface moves in an arc, delivering energy to a related energy transfer surface on the print hammer. The print hammer goes into pivoted free-flight when the armature strikes a stop pad. There is mimimum sliding, and thus minimum wear, between the energy transfer surfaces of the print hammer and armature as they both move in arcs of similarly convex circles which remain tangent at their contact point. The two-lever print actuator provides a low mass print hammer with a short contact time; the hammer moves at a substantially higher velocity than the armature at the pole face due to the optimized lever length ratios.

What is claimed is: 
     
       1. A double pivot two-lever free-flight electromagnetic print actuator assembly for impact printing of print media characterized by (a) a print hammer pivot shaft (2);   (b) an end-pivoted free-flight print hammer (1), mounted on said print hammer pivot shaft (2), having a print impact mass (3) at the end opposite the pivot and a print hammer energy transfer surface (4) between said print impact mass and said pivot;   (c) an armature pivot shaft (9) at a finite distance from said print hammer pivot shaft (2);   (d) a pivoted bellcrank armature (5) made up of an electromagnetic energy receiving mass on a finite length, finite mass coil leg (12), and an armature energy transfer surface (7) on an energy transfer leg (11), said energy transfer leg having a small mass as contrasted to said finite mass, and being relatively long as contrasted to said finite length, said armature (5) being juxtaposed at rest in contact with said print hammer (1);   said armature pivot shaft (9), said print hammer pivot shaft (2), and said print hammer and armature energy transfer surfaces (4, 7) being aligned in the sequence listed and being aligned substantially coplanar during a substantially instantaneous energy transfer from said pivoted bellcrank armature to said print hammer prior to free-flight before impact with the print media, and said print hammer energy transfer surface (4) and said armature energy transfer surface (7) lying in epitangent similarly convex circular arcs during said substantially instantaneous energy transfer, thereby minimizing both rubbing and radial stray of the point of contact of said energy transfer surfaces (4,7) with respect to said epitangent similarly convex circular arcs.   
     
     
       2. A pivoted armature, pivoted print hammer print actuator assembly having a stator block subassembly carrying energizing coils and stators and providing a base defining a rest position adjacent to a print impact position, and having a locating plate subassembly including a number of stops 10, one for each armature position characterized by (a) a print hammer pivot shaft (2), mounted in the locating plate subassembly, its axis defining a print hammer center of rotational travel;   (b) a plurality of pivoted free-flight print hammers (1) each having a face end and a pivot end, each having its pivoted end mounted on said print hammer pivot shaft (2) and having a print hammer energy transfer surface at a distance from its pivoted end;   (c) an armature pivot shaft (9), mounted in the stator block subassembly, parallel to said print hammer pivot shaft (2), its axis defining an armature bellcrank center of rotation;   (d) a plurality of pivoted bellcrank armatures (5), mounted on said armature pivot shaft (9), each having a high mass coil leg (12) of finite length (d) for receiving electromagnetic energy and converting it to kinetic energy of motion about the armature pivot axis, having a relatively small mass, relatively long, as contrasted to said coil leg, energy transfer leg (11) of length (c) between 1.5-2.0 said finite length (d) for transferring kinetic energy via motion about the armature pivot axis, having an armature energy transfer surface (7) and a stop surface on said energy transfer leg (11), said stop surface being located a first radial distance from the armature pivot axis, and said armature energy transfer surface 7 being located a second radial distance from the armature pivot axis, said second radial distance being greater than said first radial distance, said bellcrank armature (5) thus being free to rotate in a circle about its pivot, transferring kinetic energy to said print hammer (1) via said armature energy transfer surface (7) and said print hammer energy transfer surface (4) between limits of rest position and stop position where said armature (5) stop surface strikes the related stop (10), after which said print hammer (1) continues in rotational free flight about its pivot axis (2) until it impacts the print media;   (e) print actuator assembly means locating said print hammer pivot shaft (2) and said armature bellcrank pivot shaft (9) in juxtaposition which at rest locates said energy transfer surface (4) substantially coplanar with said print hammer pivot shaft (2) and said armature pivot shaft (9).   
     
     
       3. A pivoted armature, pivoted print hammer print actuator assembly according to claim 2 further characterized in that said stator block subassembly (5 to 7, 9, 11 to 18) and said locating plate subassembly (1 to 4, 10, 19 to 21) each have a plurality of locating recesses for laterally positioning said armature (5) and said print hammer (1) while allowing rotation.